Let me be completely clear about this: this feature will not go into Plank trunk. I feel that Intellihide is a sufficient option. I was actually planning on removing Autohide from Plank in the near future.

The goal of Plank is to keep it as simple as possible. Less is better. It may not please everyone, but that is not the point of the project and just a trade-off that must be made.

Rico: You are more than free to implement this (or anyone else can), however it will not merge into trunk. If Elementary OS wants this feature in Plank, they will have to maintain a patch, build a custom binary and ship that.